edward t, thanks for the info regarding potential "harness R&R".
If my continuity tests show an open circuit in the harness I will likely petition my boss to let us go that route if Komatsu is receptive to letting us have the harness "at cost".
As to "tampering" with wiring: When we received this truck, it was evident (to me) that it had been in the hands of a "butcher"
(or as one of my colleagues calls them "rip, schitt, bang" artists) because the dash harness was not secured in place by any of the OEM bend tabs and all of the OPSS (KOPS) relays were hanging down like a cluster of grapes on top of the left tilt cylinder. The dashboard panels were missing most of their mounting bolts and the small filler panel under the monitor was not even found. Also about 80 % of the plastic wire loom anchors have been cut with snips and no attempt at re-securing anything can be seen.
And..........the large and small harness connectors at the ECU have snap-in covers concealing the back side of the connector body (where the wire terminal pins are inserted). These OEM covers are supposed to be secured to each harness end with plastic zip ties..............neither of those covers on this truck are attached to the harness.......and about 1/4 of the small cover has been broken off.
I get the feeling I am actually chasing an "old problem" instead of a new one.
I will do continuity testing and if I find an open circuit I will proceed to contact Komatsu before trying to ID the cause of the open. If Komatsu is not agreeable about a new harness at cost..........I will then try to determine the reason for the circuit being open. In order to physically check the integrity of each wire where it enters the back side of the harness connector I would need to unwrap a few inches of tape in order to have enough "slack" to tug on the individual wires to check for breakage.
I do smear some dielectric compound on the connectors prior to mating them.
As an aside remark: I had to replace both the dash harness and the main chassis harness on another copy of this same truck back in May of '12. That was another case wherein the truck was sent to us from another location for us to fix.
It was a catastrophic scenario caused by somebody, somewhere, sometime in the past had decided to create an unauthorized (and ill advised) new circuit for some unknown reason by inserting the twisted bare end of a run of 10 gauge wire (THHN no less) into the back of the fuse box of the "battery hot" buss. This wire was routed along side the chassis harness coming down past the left tilt cylinder and simply laid loose along side the left cab frame member.
This wire had apparently gotten between the metal floorboard panel and the cab frame and shorted out.
I'm pretty sure that shorting event vaporized the OEM fusible link in the cab feed tap at the starter solenoid lug because the OEM Komatsu fusible link had been replaced with.........a hand made eyelet terminal and spade terminal and 3 " of 12 gauge wire.
So if my suspicions are right about that, the idiots may have been given 1 chance to "do right" and get rid of the shorting wiring, but instead they chose to eliminate a safety item (fuse link) and the stage was set in grand fashion for the next shorting event with the improper "hot wire" jammed into the fuse box buss. And SHORT it did!
With the fusible link out of the circuit......the wiring inside the dash and chassis harnesses began sagging and at some point a small ground wire got into contact with the big cab feed battery hot conductor. That must have been a flash point because I opened up the entire length of the dash harness and most of the chassis harness and it was all a very melted mess. The 2 harnesses cost us over $1,800 in parts alone. (I just tried to submit my response and was informed it was too long. So I am breaking it into 2 posts. It may end up with a "discontinuous" flavor.)